Context: Few data exist on sex- and age-specific incidence and prevalence of idiopathic hyperprolactinemia and prolactinomas. Objectives: Our objective was to assess incidence and prevalence of dopamine agonist-treated hyperprolactinemia by age and sex. Design: From the PHARMO network, we identified an open cohort of patients who were ever dispensed dopamine agonists for hyperprolactinemia. The network includes complete medication histories for more than 2 million community-dwelling residents. Prolonged use of low-dose dopamine agonist is a reliable marker for hyperprolactinemia, provided that use for Parkinson's disease and lactation withdrawal is excluded. Diagnoses were verified by prolactin values in a random subsample using the same network. Results: We identified 11,314 subjects with at least one dispensing of dopamine agonist in the period 1996-2006, of whom 1607 subjects were considered to have dopamine agonist-treated hyperprolactinemia based on the prescribing pattern. The majority of patients were women (n = 1342, 84%). The diagnosis proved to be incorrect in only 1.5% of a random subsample. The estimated incidence rate of dopamine agonist-treated hyperprolactinemia for women was 8.7/100,000 person-years and for men 1.4/100,000 person-years. The highest incidence rate was found in women 25-34 yr of age: 23.9/100,000 person-years. The mean prevalence of ever treated female patients was almost five times higher (93.9/100,000) compared with male patients (19.6/100,000). Conclusion: The incidence rates and the prevalence of dopamine agonist-treated hyperprolactinemia showed an overall preponderance in women, with a strong peak for women aged 25-34 yr. In men, no peak was found. Copyright